Week 1, Lecture 2

Cellular Form and Function

Reference Book:

Anatomy & PhysiologyThe Unity Of Form And Function

Ninth Edition;Kenneth S. Saladin

Lecture delivered by

Dr Vini Gautam

Lecturer

Department of Biomedical Engineering

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Lecture Outline

Quick Quiz

Quick Quiz

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Introduction

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Common Cell Shapes

An illustration shows 9 types of common cell shapes.

About 200 types of cells in human body with varied shapes

Note: A cell’s shape can appear different if viewed in a different type of section (longitudinal versus cross section)

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Cell Sizes

Human cell sizes

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The Relationship Between Cell Surface Area and Volume

An illustration shows how cell surface area and volume are correlated.
An illustration shows how cell surface area and volume are correlated.

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Two photos show two types of electron micrographs at same magnification of white blood cells.
Two photos show two types of electron micrographs at same magnification of white blood cells.

a: © AlvinTelser/McGraw-Hill Education;b: ©BiophotoAssociates/Science Source

How does a cell look like under a microscope?

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Basic Components of a Cell

1. Plasma (cell) membrane

2. Cytoplasm

Extracellular fluid (ECF)

An illustration shows the structure of a cell.

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1. The Plasma Membrane

Plasma membrane = border of the cell

A transmission electron microscope shows the plasma membrane between two adjacent cells.

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The Plasma Membrane

An illustration shows the molecular structure of plasma membrane.

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A transmission electron microscope shows the plasma membrane between two adjacent cells.

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Plasma membrane component #1 : Lipids (98%)

An illustration shows the molecular structure of plasma membrane.

Phospholipids

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Membrane Lipids

Cholesterol

Glycolipids

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Membrane proteins

Integral proteinspenetrate membrane

Peripheral proteins

Plasma membrane component #2 : Proteins (98%)

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Transmembrane Proteins

An illustration shows transmembrane proteins.

Figure 3.6

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Functions of different Membrane Proteins

An illustration shows some functions of membrane protein.

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To ‘stick’ cells inplace

What kind of cellam I?

Involved in the action of drugs

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A Second-Messenger System

An illustration shows a second-messenger system.

Figure 3.8

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Functions of different Membrane Proteins

An illustration shows some functions of membrane protein.

Involve TRANSPORT across the plasma membrane

Crucial to nerve and muscle function

© McGraw Hill

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Break (2 min)

See poll for a quick quiz and answer

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Functions of different Membrane Proteins

An illustration shows some functions of membrane protein.

Involve TRANSPORT across the plasma membrane

Crucial to nerve and muscle function

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Membrane Transport

Plasma membrane (and organelle membranes) areselectively permeableallowing some things through, butpreventing others from passing

Passivetransport requireno energy(ATP)

Activetransportconsume energy(ATP)

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Passive transport method #1:Filtration

Filtrationparticles are driven through membrane byphysicalpressure

Examples

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Filtration Through the Wall of a Blood Capillary

An illustration shows the filtration process in the blood capillaries.

Figure 3.13

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Passive transport method #2:Diffusion

Simple diffusionnet movement of particles from place ofhigh concentration to place of lower concentration

Substances diffuse down theirconcentration gradient

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What can affect Diffusion?

Factors affectingdiffusion ratethrough a membrane

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Passive transport method #3:Osmosis

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Passive transport method #3:Osmosis

Osmosisnetflow of waterthrough a selectively permeablemembrane

Crucial consideration for IV fluids

Osmotic imbalances underlie diarrhea, constipation, edema

Cool fact:While water can diffuse through phospholipid bilayers,osmosis is enhanced by aquaporins (channel proteins in membranespecialized for water passage)

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Tonicity

Tonicityability of a surrounding solution (bath) to affect fluid volume andpressure in a cell

Hypotonic solutioncauses cell to absorb water and swell

Hypertonic solutioncauses cell to lose water and shrivel (crenate)

Isotonic solutioncauses no change in cell volume

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Effects of Tonicity on RBCs

Three electron micrographs show the effect of tonicity in red blood cells.
Three electron micrographs show the effect of tonicity in red blood cells.
Three electron micrographs show the effect of tonicity in red blood cells.

(a-c): © David M. Philips/Science Source

Swollen cell

Crenated cell

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Osmolarity

One osmole (osm) = 1 mole of dissolved particles

Osmolarity = number of osmoles per liter of solution

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Carrier-Mediated Transport

Transport proteins in membrane carry solutes into or out ofcell (or organelle)

Specificity

Saturation

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Carrier-Mediated Transport2

Three kinds of carriers

Three mechanisms of carrier-mediated transport

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1. Facilitated Diffusion

Facilitated diffusion: a carrier moves solute down itsconcentration gradient

Does not consume ATP

Solute attaches tobinding siteon the carrier, carrier changesconformation, then releases solute on other side ofmembrane

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Facilitated Diffusion

Three illustrations demonstrate facilitated diffusion.

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2. Primary active transport across a carrier protein

Examples:

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= resting potential

The sodiumpotassium pump (Na+− K+pump)

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The SodiumPotassium Pump (Na+K+)

An illustration shows the sodium-potassium pump.

Each Na-K pump cycle:

Takes 2 K+in

-Moves ions fromlow concentration tohigher concentration

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Na+− K+pump functions

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3. Secondary active transport

Secondary active transport

An illustration shows the secondary active transport.

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Functions of different Membrane Proteins

An illustration shows some functions of membrane protein.

Involve TRANSPORT across the plasma membrane

Crucial to nerve and muscle function

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Vesicular Transport

Vesicular transportmoves large particles, fluid droplets, ornumerous molecules at once through the membrane

Vesicles = bubble-like enclosures of membrane; utilizes motorproteins energized by ATP

Endocytosisvesicular processes that bring material into cell

Exocytosisdischarging material from the cell

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Endocytosis and exocytosis

© McGraw Hill

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Break (2 min)

See poll for a quick quiz and answer

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The cell interior

An illustration shows the structure of a cell.

Note: A complete summary of cellular components can be found inTable 3.4in the reference book

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1. The Cytoskeleton

Cytoskeletonnetwork of protein filaments and cylinders

Composed of: microfilaments, intermediate fibers,microtubules

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The Cytoskeleton

An illustration and a fluorescence microscopic view shows the cytoskeleton.

Microfilaments

Intermediate filaments

Microtubules

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2. Inclusions (are not cell organelles)

Two kinds of inclusions

Never enclosed in a unitmembrane

Not essential for cell survival

An illustration shows the structure of a cell.

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3. Cell Organelles

Internal structures of a cell,carry out specialized metabolictasks

Membranous organelles

Non-membranous organelles

An illustration shows the structure of a cell.

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Endoplasmic Reticulum

An illustration shows the structure of both rough and smooth endoplasmic reticulum.

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Golgi Complex

Golgi complexa system of cisternsthat synthesizes carbohydrates andputs finishing touches on proteinsynthesis

An illustration shows the Golgi complex.

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Lysosomes

Lysosomespackage of enzymes bound by a membrane

Functions

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Mitochondria

An illustration and an electron micrograph show a mitochondrion.

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The Nucleus

Nucleususually largest organelle (~ 5μmin diameter)

Nuclear envelope: perforated by nuclearpores formed by rings of proteins

Nucleoplasmmaterial in nucleus

Two illustrations show the structure of the nucleus.

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Topics covered today

Cells, shapes and sizes

Basic components of a cell

Plasma membrane

Membrane transport

Cytoskeleton

Organelles

Inclusions

Nucleus

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Topics to be covered in the next lecture

Kinds of tissues in human body:

Epithelial tissue

Connective tissue

Nervous and Muscular (excitable) tissue

Tissue growth

Tissue development

Stem cells

Tissue repair and degeneration

Stem cell therapy, regenerative medicine, tissue engineering